In refueling a vehicle a fuel nozzle is inserted into a filler pipe leading to the fuel tank for the vehicle and fuel under pressure is discharged through the nozzle into the filler pipe, with fuel flow controlled by a suitable valve, often manually controlled. Thus, in refueling an automobile or other vehicle with, for example, gasoline, a fuel nozzle is inserted into the vehicle filler pipe and gasoline is discharged through the nozzle and into the fuel tank communicating with the filler pipe, while the operator either holds a valve manually open, or quite frequently utilizes an automatic shutoff device for terminating fuel flow as the fuel tank reaches a full configuration.
Typically in such operations, since the fuel is usually extremely volatile, a portion will evaporate and the resulting fumes escape into the atmosphere through the space between the exterior surface of the fuel nozzle and the interior surface of the filler pipe. To avoid the resultant pollution certain remedies have been proposed.
For example, U.S. Pat. No. 3,903,942 discloses a vapor seal for a fuel tank filler tube in which a so called "adapter member" is mounted in an upper end of the filler tube and constructed of an resilient, fuel resistant material, such as Neoprene, Nitrile, Viton, Buna N, or similar material. The adapter member has a constricted opening at its inner end, so that as the fuel nozzle is inserted into the filler tube the constricted lower end of the adapter member engages the outer surface of the fuel nozzle to seal the space that would normally exist between the fuel nozzle and the filler pipe.
It would appear that with this construction substantial stretching of the adapter member is required each time the fuel nozzle is inserted, which may lead to premature material fatigue, and that the adapter member can be easily sheared at the point it is attached to the filler tube if, as the fuel nozzle is inserted, it strikes the adapter member at that point.
Another proposal to obviate the problem of vapor escape during refueling consists of a resilient member formed of rubber or similar, fuel resistant material, seated on a mounting bracket attached to the upper end of a filler pipe of a vehicle. This device also includes an umbrella valve portion which normally closes a vent hole formed in the mounting bracket, but permits venting when some predetermined pressure is exceeded.
The seal with the outside of the fuel nozzle is effected by a constricted lower end of the device, generally similar to the manner in which the adapter member described above functions. While this latter device does include an umbrella valve section to permit venting, because the nozzle engaging portion is positioned on the lower end of the device, as the fuel nozzle is rocked into positions other than perfectly concentric with the filler pipe, the preloading of the umbrella valve will be reduced substantially, permitting premature venting, or in extreme cases, unseating of the umbrella valve.
Additionally, because the sealing portion of the device is positioned downstream of an annular groove formed in the exterior surface of the device to receive a seat formed on the seal mounting bracket, the device is particularly susceptible to shearing damage in the vicinity of the groove as the device is struck by the leading end of the fuel nozzle when it is thrust into the filler pipe.